We have developed several models to investigate the changes in cancer incidence and growth with age. An animal model using nude mice to grow human prostate, and small cell lung carcinoma cells employs extracellular matrix to stimulate tumor growth allowing anti-tumor agents to be tested. The same matrix proteins were shown to also enhance tumor growth in older animals perhaps by overcoming host immune defense. A quantitative angiogenesis assay was developed to measure the role of neovascularization in tumor growth and atherosclerosis. Using this assay, inhibitors and promoters of angiogenesis were identified. Vascular smooth muscle cells inhibit the angiogenic response suggests that they secrete inhibitors. We have also developed a rat model for spontaneous, mammary neoplasms by isolating cells from spontaneous breast tumors of aged rats which will be used to assess genetic alterations associated with aging and tumorigenesis.